The invention resides in the field of mechanics or mechanical engineering and precision engineering and can be used in particular in the construction of small instruments for invasive use in medical technology.
Instruments which can be actuated from outwith the body via flexible shafts are often used in particular in minimally invasive medicine. These shafts are normally guided through catheters which are introduced into the body through small openings or naturally occurring body vessels under particularly sensitive surrounding conditions.
A particular application form resides for example in the actuation of liquid pumps in microconstructional form which are used for example as heart pumps and which can be introduced into a ventricle with a heart catheter.
Particular requirements thereby reside not only in the small constructional size of the corresponding pumps, as also when using other microinvasive instruments actuated via such a shaft, but also during operation of the flexible shaft. In particular at the high speeds of rotation often required, intensive deformation of the shaft takes place which causes high mechanical and thermal stress. Therefore it is normal to fill corresponding hollow catheters with a biocompatible liquid for lubrication and cooling of the shaft.
In order to ensure shielding of such a hollow catheter relative to the body exterior, frequently motor drives with magnetic couplings are used as drives at the proximal end of the shaft, externally of the body, which drives act through hermetically sealed housing walls of corresponding shaft connection housings.
Magnetic couplings of this type are however substantially more expensive and sensitive relative to conventional couplings. In order to transmit the required torque reliably, a significant over-dimensioning is required because of the normally low efficiency of such a magnetic coupling.
In addition, normally the motor drive together with the hollow catheter and the shaft and possibly a connected instrument must be certificated. This is particularly inefficient if at least one of the parts, either the motor drive or the catheter, is intended to be used multiple times and if these are only assembled during actual use.
In connection with a hollow catheter which houses a guide wire and a rotating imaging ultrasonic device, sterile shielding of an end region of a slowly rotating shaft is known from the U.S. Pat. No. 5,368,035, which shaft essentially comprises a sleeve and is assembled with the hollow catheter if required or is again detached from the latter in order to push an element via the guide wire. The sleeve prevents toxic substances from passing through in that it forms a mechanical obstacle for these substances.